1. Field of the Invention
The present invention relates to a lens drive apparatus for use in a disc player for writing information onto discs and reading recorded information, and more particularly to the configuration of a lens driving apparatus employing plane coils.
2. Description of Related Art
There is a known lens driving apparatus that drives an objective lens in the direction of the optical axis (in the direction of focus) to condense onto the surface of a disc a beam for reading information that has been optically recorded thereon. The lens driving apparatus also drives the objective lens in a direction perpendicular to the optical axis of the lens to allow the read beam to follow information tracks.
It is desirable that movable portions constituting the lens driving apparatus are small in size and light in weight. As shown in FIG. 1A, available was a coil bobbin type 5 in which focus coils 3 and tracking coils 4 are wound on a coil bobbin 2 having an objective lens 1 built therein. A print coil type 8 as shown in FIG. 1B has been suggested (for example, in Japanese Patent Laid-Open Publication No.Hei 8-203103) in place of the coil bobbin type 5. The print coil type 8 has flat coil boards 7 fixed with adhesive or the like to both sides of a holder 6 having the objective lens 1 built therein, the coil boards 7 being prepared by patterning and etching the focus coils 3 and the tracking coils 4.
However, with the coil boards 7 suggested in Japanese Patent Kokai No. 8-203103, the focus coils 3 are provided with a drive force in the direction of focus (shown by arrow F) by being arranged across the N- and S-poles of a magnet 9, as shown in FIG. 1C. Two tracking coils 4 are located on the N-pole of the magnet 9 and the other two tracking coils 4 are located on the S-pole of the magnet 9. In addition, about only a quarter of each of the tracking coils 4 is placed within the magnetic field of the magnet 9 (in the direction shown by arrow T in the figure of tracking). Thus, the tracking coils 4 formed in four are provided with a drive force in the tracking direction. Accordingly, the coil boards 7 of the print coil type 8 needed to be adapted to substantially extend sideward from the outer dimensions of the magnet 9 in the tracking direction. In addition, the effective magnetic field of the magnet 9 for the tracking coils 4 was reduced and the coil boards 7 were made larger than the outer dimensions of the magnet 9.
The present invention has been developed in view of the aforementioned problems. An object of the present invention is to provide a lens driving apparatus that effectively makes use of the magnetic flux of a magnet and can provide coil boards reduced in size.
Another object of the present invention is to provide a lens driving apparatus that has a reduced number of coils, thereby providing coil boards reduced in size and cost.
To solve the aforementioned problems, a lens driving apparatus according to a first aspect of the present invention comprises a lens holder supported movably in directions of focus and tracking, and focus and tracking drive coils, mounted to the lens holder. The device also comprises magnetic flux imparting means for imparting a magnetic flux to the focus and tracking drive coils. The lens driving apparatus is characterized in that the focus and tracking drive coils each include a pair of plane coils, formed in planes perpendicular to a direction of jitter and having a coil axis parallel to the direction of jitter substantially perpendicular to the directions of focus and tracking. The lens driving apparatus is also characterized in that the magnetic flux imparting means impart magnetic fluxes in directions opposite to each other along the direction of jitter to two areas of the plane coils divided by imaginary lines inclined relative to the directions of both focus and tracking. The lens driving apparatus is further characterized in that the imaginary lines of the pair of plane coils each are arranged symmetrically with respect to a plane parallel to the direction of jitter and including an optical axis.
In addition, a lens driving apparatus according to a second aspect of the present invention is the aforementioned lens driving apparatus, characterized in that the magnetic flux imparting means include magnets opposite to the plane coils, the magnets having different magnetic poles opposite to each of the two areas.
Furthermore, a lens driving apparatus according to a third aspect of the present invention is the lens driving apparatus according to the first feature. The lens driving apparatus is characterized in that the magnetic flux imparting means are arranged opposite to the plane coils and include magnets having magnetic pole surfaces perpendicular to the direction of jitter, and the magnetic pole surfaces have different magnetic poles sitting on areas bounded by the imaginary lines.
Furthermore, a lens driving apparatus according to a fourth aspect of the present invention is any one of the aforementioned lens driving apparatuss. The lens driving apparatus is characterized in that the pair of plane coils constituting the focus drive coil each are supplied with drive currents in the same direction. On the other hand, the pair of plane coils constituting the tracking drive coil each are supplied with drive currents in directions opposite to each other.
Furthermore, a lens driving apparatus according to a fifth aspect of the present invention is any one of the aforementioned lens driving apparatuss according to the first to third aspect of the present invention. The lens driving apparatus is characterized in that the pair of plane coils constituting the focus drive coil each are supplied with drive currents in directions opposite to each other. On the other hand, the pair of plane coils constituting the tracking drive coil each are supplied with drive currents in the same direction.
Furthermore, a lens driving apparatus according to a sixth aspect of the present invention is any one of the aforementioned lens driving apparatuss. The lens driving apparatus is characterized in that the pair of plane coils constituting the focus drive coil and the pair of plane coils constituting the tracking drive coil are formed in the same in-plane shape, being arranged one on the other along the direction of jitter.
Furthermore, a lens driving apparatus according to a seventh aspect of the present invention is any one of the aforementioned lens driving apparatuss. The lens driving apparatus is characterized in that the pair of plane coils constituting the focus drive coil each generate drive forces to yield a resultant focus drive force. On the other hand, the pair of plane coils constituting the tracking drive coil each generate drive forces to yield a resultant tracking drive force.
Furthermore, a lens driving apparatus according to an eighth aspect of the present invention comprises a lens holder having a bearing hole to be fitted to a shaft extending in a direction of focus, made slidable along and rotatable about the shaft. The lens driving apparatus also comprises focus and tracking drive coils, mounted to the lens holder, and magnetic flux imparting means for imparting a magnetic flux to the focus and tracking drive coils. The lens driving apparatus is characterized in that the focus and tracking drive coils each are adapted to include a pair of plane coils having a coil axis perpendicular to a direction of focus. The lens driving apparatus is also characterized in that the magnetic flux imparting means impart magnetic fluxes in directions opposite to each other to two areas of the coils divided by imaginary lines inclined relative to the directions of both focus and tracking. The lens driving apparatus is further characterized in that the imaginary lines of the pair of coils each are arranged symmetrically with respect to a plane including the axis.
The aforementioned lens driving apparatus comprises a lens holder supported movably in directions of focus and tracking, and focus and tracking drive coils, mounted to the lens holder. The device also comprises magnetic flux imparting means for imparting a magnetic flux to the focus and tracking drive coils. The focus and tracking drive coils each are adapted to include a pair of plane coils, formed in planes perpendicular to a direction of jitter and having a coil axis parallel to the direction of jitter substantially perpendicular to the directions of focus and tracking. The magnetic flux imparting means are adapted to impart magnetic fluxes in directions opposite to each other along the direction of jitter to two areas of the plane coils divided by imaginary lines inclined relative to the directions of both focus and tracking. The imaginary lines of the pair of plane coils each are arranged symmetrically with respect to a plane parallel to the direction of jitter and including an optical axis. Accordingly, supplying a drive current to each of the pair of plane coils, which constitute the focus drive coil, in the same direction will cause the lens holder to be driven in the direction of focus. On the other hand, supplying a drive current to each of the pair of plane coils, which constitute the tracking drive coil, in directions opposite to each other will cause the lens holder to be driven in the direction of tracking.
To solve the aforementioned problems, a lens driving apparatus according to a ninth aspect of the present invention comprises a lens holder supported movably in directions of focus and tracking. The device also comprises drive coils, mounted to the lens holder, for generating a drive force in a direction of focus and a drive force in a direction of tracking to yield a resultant drive force, and magnetic flux imparting means for imparting a magnetic flux to the drive coils. The lens driving apparatus is characterized in that the drive coils each comprise a pair of coils arranged symmetrically with respect to a plane including an optical axis and perpendicular to the direction of tracking. The device is also characterized in that the magnetic flux imparting means impart magnetic fluxes in directions opposite to each other along the direction of jitter to two areas of the coils divided by imaginary lines inclined relative to the directions of both focus and tracking. The device is further characterized in that one of the pair of coils is supplied with an additive current of focus and tracking drive currents, whereas the other is supplied with a differential current of the focus and tracking drive currents.
Furthermore, a lens driving apparatus according to a tenth aspect of the present invention is the lens driving apparatus according to the ninth aspect of the present invention. The device is characterized by arranging the pair of coils in the same plane perpendicular to the direction of jitter.
Furthermore, a lens driving apparatus according to an eleventh aspect of the present invention is the lens driving apparatus according to the ninth aspect of the present invention. The device is characterized in that the pair of coils are plane coils provided on the same printed board parallel to a plane perpendicular to the direction of jitter.
Furthermore, a lens driving apparatus according to a twelfth aspect of the present invention is any one of the lens driving apparatuss according to the ninth to eleventh aspect of the present invention. The device is characterized in that the magnetic flux imparting means include magnetic pole surfaces opposite to the drive coils, the magnetic pole surfaces having different magnetic poles corresponding to the two areas.
Furthermore, a lens driving apparatus according to a thirteenth aspect of the present invention comprises a lens holder supported movably in directions of focus and tracking. The device also comprises drive coils, mounted to the lens holder, for generating a drive force in a direction of focus and a drive force in a direction of tracking to yield a resultant drive force, and magnetic flux imparting means for imparting a magnetic flux to the drive coils. The lens driving apparatus is characterized in that the drive coils comprise a first and second coil each arranged in a first plane perpendicular to a direction of jitter and symmetrically with respect to a plane including an optical axis and perpendicular to the direction of tracking. Here, a third and fourth coil each are arranged in a second plane parallel to the first plane and symmetrically with respect to a plane including the optical axis and perpendicular to the direction of tracking. A group of the first and second coils and a group of the third and fourth coils each are arranged symmetrically with respect to the optical axis. Said magnetic flux imparting means are adapted to impart magnetic fluxes in directions opposite to each other along the direction of jitter to two areas of the coils divided by imaginary lines inclined relative to the directions of both focus and tracking. Moreover, one of the first and second coils is supplied with an additive current of focus and tracking drive currents, whereas the other is supplied with a differential current of the focus and tracking drive currents. Of the third and fourth coils, a coil opposite to the one of the first and second coils supplied with the additive current is supplied with the differential current, whereas the coil opposite to the other coil supplied with the differential current is supplied with an additive current.
Furthermore, a lens driving apparatus according to a fourteenth aspect of the present invention is the aforementioned lens driving apparatus, characterized in that the first and second coils are provided on the same printed board parallel to a plane perpendicular to the direction of jitter. On the other hand, the third and fourth coils are provided on the same printed board parallel to a plane perpendicular to the direction of jitter.
Furthermore, a lens driving apparatus according to a fifteenth aspect of the present invention is any one of the aforementioned lens driving apparatuss according to the ninth to fourteenth aspect of the present invention. The lens driving apparatus is characterized in that the imaginary lines are inclined at 45 degrees relative to both the directions of focus and tracking.
Furthermore, a lens driving apparatus according to a sixteenth aspect of the present invention comprises a lens holder having a bearing hole to be fitted to a shaft extending in a direction of focus, made slidable along and rotatable about the shaft. The device also comprises drive coils, mounted to the lens holder, for generating a drive force in a direction of focus and a drive force in a direction of tracking to yield a resultant drive force, and magnetic flux imparting means for imparting a magnetic flux to the drive coils. The lens driving apparatus is characterized in that the drive coils each comprise a pair of coils, arranged symmetrically with respect to a plane including the shaft, having a coil axis perpendicular to a direction of focus. The lens driving apparatus is characterized in that the magnetic flux imparting means impart magnetic fluxes in directions opposite to each other to two areas of the coils divided by imaginary lines inclined relative to the directions of both focus and tracking. The lens driving apparatus is further characterized in that one of the pair of coils is supplied with an additive current of focus and tracking drive currents, whereas the other is supplied with a differential current of the focus and tracking drive currents.
The lens driving apparatus according to the ninth to sixteenth aspect of the present invention comprises a lens holder supported movably in directions of focus and tracking. The device also comprises drive coils, mounted to the lens holder, for generating a drive force in a direction of focus and a drive force in a direction of tracking to yield a resultant drive force, and magnetic flux imparting means for imparting a magnetic flux to the drive coils. The lens driving apparatus is configured such that the drive coils each comprise a pair of coils arranged symmetrically with respect to a plane including an optical axis and perpendicular to the direction of tracking. The device is also configured such that the magnetic flux imparting means impart magnetic fluxes in directions opposite to each other along the direction of jitter to two areas of the coils divided by imaginary lines inclined relative to the directions of both focus and tracking. The device is further configured such that one of the pair of coils is supplied with an additive current of focus and tracking drive currents, whereas the other is supplied with a differential current of the focus and tracking drive currents. Accordingly, it is made possible to reduce the number of coils when compared with prior art devices, thereby implementing a reduction in cost and size.